Low Cost Geothermal Greenhouse Heating System for Southern Climates

Low Cost Geothermal Greenhouse Heating System for Southern Climates

Summary

We have completed all necessary ground work and installed the low-cost geothermal heating system and made modifications to allow for continuous operation. A severe drought from October through December (0.57 inches of rain, compared to the normal 10.63 inches), prevented us from utilizing the system, since the system relies on our pond to store and transfer heat. We have given 3 farm tours where the system was demonstrated and discussed. A graduate student at Texas A&M University has also joined the project as a collaborator who will assist with data collection and analysis over the next two years. The objectives of the project have also been expanded to include measurements of root-zone cooling effects of the system when ran during the hot spring/summer months.

Objectives/Performance Targets

• – Drain pond, excavate for installation
  – Install geothermal system
  – Purge, make modifications and run system
  – Take Measurements on performance of system
  – Report results

Accomplishments/Milestones

We began draining the pond after the field crops were finished in August as planned; rains in early September caused delays in completely draining the pond, which was fully accomplished in mid-October. We hired a bulldozer to excavate the pond to increase our water holding capacity to approximately 860,000 gallons (Fig. 1). Once the excavation was complete we dug trenches approximately 6’ deep from the pond to the greenhouse and included a separate trench from the greenhouse back to the pond. We then installed the system in early November (Fig. 2-4). Once the installation was complete, we had to make some modifications to purge all the air from the system (we installed a city water line with a valve and back-flow preventer to fill the system, and added a foot-valve on the uptake side of the system in the pond to replace of the air vent). A lack of significant rainfall prevented us from utilizing the system during 2010, since there was no water in the pond to store heat from the greenhouse.
We have decided to expand our objectives to include measurements to monitor the performance of the system as a root-zone cooling system in the hot months to see if cooling the root-zone will have an impact on tomato production in our climate during the summer.

• Figure 2. Installing the Heat Exchanger in Pond
• Figure 3. Completed Heat Exchanger in Pond
• Figure 1. Pond Excavation
• Figure 4. Heat Exchanger in Greenhouse

Impacts and Contributions/Outcomes

Even though we have not been able to measure the impacts of our system yet, we have already given three farm tours where the geothermal system has been discussed. Two of the tours were course field trips for Texas A&M students: HORT325, Vegetable Crop Production and GEOG489, Geography of food. The third farm tour was for the Brazos Locavores, a local group dedicated to supporting local businesses.
A Texas A&M graduate student has also agreed to take on the data collection and analyses to measure the impact of our geothermal system on greenhouse tomato production.
While we still don’t know the outcome of our system or how it will impact greenhouse tomato production, it has initiated numerous discussions on alternative heating systems.

Collaborators: